The visual inspection of a generator field, stator and wedge tightness, as well as electrical testing, should be performed on a periodic basis. Conventional generator/stator inspection and testing procedures typically require the complete disassembly of the stator and removal of the generator field from the stator before any inspections or tests can be performed on the unit. The cost of disassembly and removal of the field, the time it takes for this process, and the dangers of field removal have lead to the omission of the generator and stator examinations from outage schedules.
In-situ inspections of generators have been performed employing poles, trolleys and field turning techniques. These procedures have not accomplished the inspection task in a completely satisfactory manner.
A miniature air gap inspection crawler is disclosed in U.S. Pat. No. 5,650,579, the contents of which are hereby incorporated by reference. In this arrangement, a miniature crawler is designed to pass through the radial air gap between the core iron and the retaining ring for in-situ inspection of the field and stator core. The crawler can be collapsed for insertion into an entrance gap of 1.125" and is driven by tracks to a selected axial location. The crawler is then expanded at a desired circumferential position in the air gap. Video cameras and other inspection tools attached to the crawler are used to perform generator field and stator core inspections in the air gap.
This inspection crawler, however, cannot be used with the many existing generators that have entrance gaps smaller than 1.125". As such, inspection of these generators requires the complete disassembly of the stator and removal of the generator field from the stator before any inspections can be performed on the unit.